Isoniazid Liver Damage: Risks, Signs, and What to Do

When you’re taking isoniazid, a first-line antibiotic used to treat tuberculosis. Also known as INH, it’s one of the most effective drugs for stopping TB—but it’s also one of the most likely to harm your liver. This isn’t just a rare side effect. About 1 in 10 people on isoniazid develop some level of liver enzyme rise, and 1 in 250 may get serious liver injury. It’s not random. Age, alcohol use, HIV status, and how long you’ve been on the drug all play a role. If you’re over 35, especially over 50, your risk goes up fast. Women, particularly those who are postmenopausal, are also more vulnerable.

What makes drug-induced liver injury, liver damage caused by medications rather than viruses or alcohol from isoniazid so dangerous is how quiet it starts. You might feel fine—no jaundice, no pain—until your liver is already struggling. That’s why routine blood tests aren’t optional. Doctors check ALT and AST levels every 4 to 8 weeks during treatment. If those numbers jump more than three times the upper limit of normal, you stop isoniazid. No waiting. No hoping it gets better. Liver damage from this drug can turn into acute liver failure in days if ignored. And it’s not just about the drug itself. Mixing isoniazid with alcohol, acetaminophen, or even certain herbal supplements like kava or green tea extract can push your liver over the edge.

Some people wonder if they should skip isoniazid because of the risk. But stopping it without medical advice is far riskier. Untreated TB kills. The key is awareness and monitoring. If you’re on isoniazid, know the red flags: unexplained fatigue, dark urine, yellow eyes or skin, nausea that won’t go away, or pain in the upper right belly. Don’t brush them off as stress or a stomach bug. These are your body’s alarms. And if you’ve had hepatitis before, or you’re on other meds that affect the liver—like statins or seizure drugs—you need to talk to your doctor about alternatives or extra monitoring. There are other TB drugs, like rifampin or ethambutol, that may be safer for you. But they’re not automatic replacements. Your treatment plan needs to be tailored.

Below, you’ll find real-world insights from people who’ve faced this exact issue. Some share how they caught the problem early. Others explain what happened when they ignored the signs. You’ll also see how compounding pharmacies help patients who can’t tolerate standard doses, and how drug interactions with common supplements can turn a safe treatment into a crisis. This isn’t theoretical. These are the stories that happen every day in clinics and homes. What you read here could help you—or someone you care about—avoid a hospital stay.